diff --git a/alembic/operations/base.py b/alembic/operations/base.py
index 649e7f2b..27dd3b9e 100644
--- a/alembic/operations/base.py
+++ b/alembic/operations/base.py
@@ -1771,7 +1771,7 @@ def create_index(
             ...
 
         def create_primary_key(
-            self, constraint_name: str, columns: List[str]
+            self, constraint_name: Optional[str], columns: List[str]
         ) -> None:
             """Issue a "create primary key" instruction using the
             current batch migration context.